In a new series of lawsuits, Hollywood studios for the first time are targeting companies that provide access to Usenet newsgroups.

This corner of the Internet, largely a leftover from the days before the Web exploded into the mainstream, rarely gets much attention. It's still primarily a forum for text discussions (and overwhelming amounts of spam), where techies help one another with Windows and driver problems, and animal lovers share cat stories.

But in the last few years, a handful of technologies have emerged that have made newsgroups a much more fertile place for downloading copies of movies, music and software. Here's a quick primer on what happens there and what the Motion Picture Association of America has done.

Q: What are newsgroups?
A: Also known as Usenet, newsgroups are one of the earliest forms of sustained conversation online. Initially started by Duke University graduate students in 1980, Usenet evolved over the years into thousands of individual newsgroups that focused on specific subjects such as dogs, science fiction authors, politics or pornography.

Readers post messages similar to e-mails to a specific group. All the content of that group is relayed through servers across the Net, and can be read with a newsgroup reader such as Forte's Agent, or inside some other Web browser and e-mail programs. Most ISPs subscribe to a newsgroup feed, though these are becoming harder to find. Google archives much of Usenet's traffic, all the way back to January 1981, at groups.google.com.

Another historical note: Before becoming a Web standby, the "frequently asked questions," or FAQ, format was widely popularized on newsgroups (though it didn't originate with them).

Q: What does this have to do with piracy?
A: Early on, people learned to send pictures, movies or even full software applications through Usenet groups by breaking the large files into small individual pieces and sending them separately. These large files, called "binaries," could be reconstructed by most newsgroup software, as long as all the pieces came through.

Q: Is this the same as file-sharing?
A: In a sense. Uploading a copyrighted file to a newsgroup is illegal, and the recording industry has targeted individual posters in the past (though largely before peer-to-peer networks emerged).

But unlike peer-to-peer networks, the files uploaded are stored in pieces on the Usenet servers around the world, not on individual computer users' hard drives.

Q: Isn't all this harder than using BitTorrent or eDonkey?
A: For most of Usenet's history, it has been much harder, and more inefficient. Big movie or software files can be broken into hundreds of individual pieces, for example, and if one or two get lost, it can make the whole movie or application unusable.

But in the last few years, several technologies have emerged to make this easier.

One, called Par files (shortened from Parity), lets big files be reconstructed even if some of the individual pieces are missing. Par files are used in other places where data transfer is unreliable, and they are becoming increasingly common on Usenet.

The other technology is an innovation similar, in a sense, to BitTorrent's torrent files. Dubbed NZB files (and created by a company called NewzBin), they automatically group together all the disparate pieces of a big binary file, allowing it to be downloaded and reconstructed with a single click.

Q: Who is the MPAA actually targeting?
A: With this round of suits, the MPAA is focusing on a small group of companies that search the Usenet feeds for movies, software, music and other files. Some of them provide the NZB files along with the search results, so the files can be instantly downloaded. Others simply provide an index of everything that's been posted to newsgroups.

Q: Are newsgroup search engines illegal, then?
A: That's a tricky question. The MPAA says all the sites they've sued are facilitating piracy. But the legal status of search engines has never quite been clarified, and indeed, Google itself is the largest newsgroup search tool in existence.

The Digital Millennium Copyright Act provides a legal shield, or "safe harbor" for search engines that meet a certain set of requirements, including the ability for copyright holders to request that links to copyrighted material be taken down.

BinNews, a Florida-based site that was sued on Thursday, contends that it doesn't provide direct links to files and in fact helps copyright holders find their works on Usenet so they can be removed. Its owner, a 31-year-old businessman named Joe (he declined to provide his last name), says he'll fight the lawsuit.

Q: Are people who have uploaded or downloaded copyrighted files from Usenet at legal risk?
A: The current lawsuits are targeting only the search engines and NZB file hubs. However, as with virtually every activity on the Internet, uploading and downloading files from Usenet does leave a trace that can be tracked back to the individual ISP and computer, if copyright holders dedicate enough resources to it.